Concept preview

What you will be able to do

1. 01Describe the structure of an amino acid and how peptide bonds join them.
2. 02Explain the four levels of protein structure and how R groups drive folding.
3. 03Explain denaturation and why it destroys a protein's function.
4. 04List the major roles of proteins and relate them to the principle that shape determines function.

If carbohydrates and lipids are the fuel and fabric of the body, the proteins are its machinery. No other class of molecule does so many different jobs: proteins speed up chemical reactions, build hair and muscle, carry oxygen in the blood, defend against disease, and pass signals between cells. Yet every one of the thousands of different proteins in your body is built from the same twenty small building blocks, the amino acids, strung together in different orders and then folded into precise three-dimensional shapes. Understanding proteins means understanding how a one-dimensional string of amino acids gives rise to a working, three-dimensional machine, and how easily that machine can be wrecked. That story runs through four levels of structure, and it begins with a single small molecule.